The motions of the retinal image resulting from involuntary eye movements supply temporal changes of illuminance over the receptors. The main purpose of the proposed research program is to determine if and how these modulations in illuminance are used by the human visual system for processing spatial and temporal information. In addition, the course of image disappearance which takes place during viewing with a motionless retinal image will be investigated with the aim of understanding the processes underlying increment thresholds, brightness discrimination and the nature of after-images. Electrophysiological experiments on the cat visual system are designed to study the unit activity under the conditions of a stationary and moving retinal image. In addition, the characteristics of the unit activity in terms of the properties of the stimulus will be explored. These experiments will be planned to complement the studies on the human visual systems. BIBLIOGRAPHIC REFERENCES: Tulunay-Keesey, U. and Jones, R.M. The Effect of Micromovements of the Eye and Exposure Duration on Contrast Sensitivity (1976) Vision Res. 16, 481-488. Tulunay-Keesey, U. The Role of Eye Movements in Maintainance of Vision. In Eye Movements and Psychological Processes, R.A. Monty and J.W. Senders, Ed., John Wiley & Sons, New York, 1976.